Cleavage Crack Research Articles

On cleavage crack morphology in some rock materials of different genesis

Fracture of rocks and biominerals on the microscopic scale under bending was examined. Eggs of some birds were used in the study because an eggshell is biomineral consisted of 90% of calcium carbonate of the biological genesis. Cracking in the model materials was studied in optical microscopes including in situ bending of eggshell samples. It was shown that despite brittle deformation behavior on the macroscopic scale and brittle transgranular fracture as fracture mode, the morphology of cracking of model materials looks like cracks in the neck of aluminum under tension.

Investigation on the Machinability of Polycrystalline ZnS by Micro-Laser-Assisted Diamond Cutting.

Polycrystalline ZnS is a typical infrared optical material. It is widely used in advanced optical systems due to its excellent optical properties. The machining accuracy of polycrystalline ZnS optical elements must satisfy the requirements of high-performance system development. However, the soft and brittle nature of the material poses a challenge for high-quality and efficient machining. In recent years, in situ laser-assisted diamond cutting has been proven to be an effective method for ultra-precision cutting of brittle materials. In this study, the mechanism of in situ laser-assisted cutting on ultra-precision cutting machinability enhancement of ZnS was investigated. Firstly, the physical properties of ZnS were characterized by high-temperature nanoindentation experiments. The result revealed an increase in ductile machinability of ZnS due to plastic deformation and a decrease in microhardness and Young's modulus at high temperatures. It provided a fundamental theory for the ductile-brittle transition of ZnS. Subsequently, a series of diamond-cutting experiments were carried out to study the removal mechanism of ZnS during in situ laser-assisted cutting. It was found that the mass damage initiation depth groove generated by in situ laser-assisted cutting increased by 57.99% compared to the groove generated by ordinary cutting. It was found that micron-sized pits were suppressed under in situ laser-assisted cutting. The main damage form of HIP-ZnS was changed from flake spalling and pits to radial cleavage cracks. Additionally, the laser can suppress the removal mode difference of different grain crystallographic and ensure the ductile region processing. Finally, planning cutting experiments were carried out to verify that a smooth and uniform surface with Sa of 3.607 nm was achieved at a laser power of 20 W, which was 73.58% better than normal cutting. The main components of roughness were grain boundary steps and submicron pit. This study provides a promising method for ultra-precision cutting of ZnS.

Effect of rare earth element Y on the crack propagation behavior of Mg alloys: A molecular dynamics simulation

The effect of the distribution and concentration of rare earth (RE) element Y, crack orientation, temperature, and strain rate on the crack propagation behavior of the Mg alloys is investigated by molecular dynamics/Monte Carlo simulations. The results show that the RE element Y tends to form locally short-range order structures in the Mg alloys, and the introduction of the RE element Y can enhance the fracture toughness of the Mg alloys. The results indicate that with the increase of Y concentration, the crack propagation mode of the Mg alloys shifts from a mode, dominated by the dislocation emissions at the crack tip and the crack cleavage propagation to a mode dominated by the solid-state amorphization and the slip of amorphous bands. In addition, the results show that the faster the strain rate, the slower the crack propagation speed, and the crack propagation resistance increases with increasing temperature.

Effect of welding method and heat treatment on the fracture toughness of low alloy steel deposited metal

The fracture toughness of the weld deposited metal plays an important role in the safe service of the reactor pressure vessel (RPV). Shielded melting arc welding (SMAW) and submerged arc welding (SAW) are two common welding methods in the construction of RPV. In this paper, the effects of the welding method and post-weld heat treatment (PWHT) on the index T0 of low-temperature fracture toughness of deposited metal were studied respectively. Through the characterization and observation of microstructure and cleavage crack initiation, the effect mechanism of the welding method and PWHT on the low-temperature fracture toughness of deposited metal was determined. The results show that the position in which oxide near the hardening phase is easy to become the cleavage crack initiation of deposited metal. The PWHT dissolves the M-A island to improve the fracture toughness of the deposited metal. The SMAW deposited metal has a smaller oxide inclusion diameter and less cementite than SAW, resulting in higher fracture toughness.

Embrittlement of notched duplex stainless steel: Role of hydrogen-assisted void growth and cleavage

The micro-degradation processes related to the ductile-brittle transition are crucial for revealing hydrogen embrittlement mechanisms. This study investigates the evolution and transition of hydrogen-assisted damages in notched duplex stainless steel using a combination of microstructural characterization, numerical simulations, and mechanistic models. The results show that the brittle area of the fracture surface increases rapidly with decreasing cathodic potential, accompanied by the fractography transition in a sequence of voids, voids mixed with quasi-cleavage, and quasi-cleavage. While hydrogen-assisted dislocation emission from the void surface and stress concentration at the phase boundary promote nanovoid growth, hydrogen-enhanced plasticity facilitates preferential void growth along the ferrite block. At higher hydrogen concentrations, ferrite cleavage cracking may originate from prolate voids and hydrogen-augmented Cottrell dislocation reactions, reducing plastic strain near the crack tip and hence diminishing the formation of vacancies as void nuclei. Previous studies have focused on the statistics of hydrogen's effect on void size. This work demonstrates the dislocation mechanism of hydrogen-assisted void growth and provides new insights into the development of micro-mechanism-based models to predict hydrogen embrittlement.

Microstructural Modification, Mechanical Properties, and Wear Behaviour of Aged Al-Si-Mg/Si3N4 Composites for Aerospace Applications

The main objective of the present research is to probe how ageing time influences the morphological, mechanical, and wear behaviour of stir cast Al-Si-Mg alloy, reinforced with 10 wt.% Si3N4 particles subsequently heat treated in T6 condition. The findings reveal that the presence of Si3N4 reinforcements, followed by the heat treatment, enhances the mechanical and tribological properties of the composite. The ensuing mechanical properties show significant improvement prior to aging heat treatment (180 °C/4h), reaching a hardness of 120.8 HV (45 % increase) and tensile strength of 275 MPa (50 % increment), respectively compared to as-cast composite. Fractography reveals dimples, transgranular cleavage surfaces, cracks, and micro-ploughing. Among the samples tested, the composite aged for 4 h (180 °C/4h, ASN-4) demonstrates the lowest wear rate. Abrasive and adhesive wear in combination is the primary wear mechanism in these samples. Overall, this research provides insights for research endeavors in manufacturing various components in the aerospace industry.

Theoretical prediction of texture requirements for improving the intrinsic cleavage crack resistance of BCC Fe

Based on the classical Rice model of crack tip dislocation emission, the present article provides a theoretical prediction of suitable grain orientations (texture components) in a rolled polycrystalline BCC Fe plate which can improve the overall resistance to cleavage crack propagation. Besides, the beneficial effect of alloying additions on further improvement in the intrinsic crack resistance of the steel is also discussed pertaining to the role of unstable stacking fault energy.

Microstructure evolution of V-containing low carbon ultra-fine bainitic steel during medium-temperature tempering and strengthening-toughening mechanism

In the present study, the microstructure evolution and the corresponding mechanical properties of V-containing low carbon ultra-fine bainitic steel during tempering were studied. The results show that during the initial stages of tempering, part of retained austenite in V-containing ultra-fine bainite steel transforms into bainite. The stability of the retained austenite improves when the tempering period is increased to 5 h. Simultaneously, nano-sized VC precipitates are precipitated in the microstructure. On the one hand, these phases can give full play to the transformation-induced plasticity (TRIP) effect by modulating the carbon content of the retained austenite. On the other hand, they can also reduce the lattice distortion in the matrix and combine it with the lower dislocation density, thereby improving the plasticity of the specimen. At the same time, the fine precipitated phase can also effectively improve the toughness of the cleavage crack region in the transition zone, preventing the micro-cracks from generating at the interface of the precipitated phase and then extending to the adjacent matrix to cause fracture, so that the uniform elongation, total elongation, impact toughness at room temperature and impact toughness at low temperature of the 5 h specimen are as high as 8.8 ± 0.2 %、16.2 ± 0.7 %、113 ± 4 J/cm2 and 76 ± 2 J/cm2, respectively. Furthermore, the primary contribution of the strengthening mechanism in the microstructure has shifted from fine grain strengthening and dislocation strengthening to precipitation strengthening, and part of the retained austenite undergoes a martensitic transformation during cooling, resulting in the highest yield strength of 1086 MPa for the 5 h specimen. The tensile strength is effectively maintained at 1402 MPa by increasing the tempering period, which has good tempering resistance, to achieve the comprehensive performance optimization of bainitic steel.

ВИНИКНЕННЯ І РОЗВИТОК ТРІЩИНОУТВОРЕННЯ В ГІРСЬКИХ ПОРОДАХ ПРИ СТАТИЧНОМУ НАВАНТАЖЕННІ

The paper examines the occurrence and development of cracks in rocks under static loads, various conditions and factors of crack initiation and development. For comparison, such rocks as concrete, granite, sandstone, plasterboard are taken. This is said to help the cracks in the rock spread in the right direction. The technology of crack formation with the help of insert plates under the action of non-explosive mixtures is considered. When modeling, the minor and major axes of the ellipse around the insert of the plate with holes are taken. Construct isolines of rock destruction at a point in the form of ellipses. Determine the most likely direction of cracks during rock destruction. The conditions for the development of cleavage cracks relative to the axes of anisotropy with maximum and minimum strength are considered. The theoretical and experimental justifications of the rational technological parameters of mining stone blocks by the hole method by the formation of a separation crack in the rock in a given direction have been studied. The determination of the plane stress state around a hole with a 5- and 8-mm-thick insert plate is studied, and equivalent stress diagrams are given. The methods of directional destruction and the occurrence of cracks in rocks when pouring non-explosive mixtures into wells and inserting cartridges with a destructive substance into wells are considered. It clearly shows the greater efficiency of using cartridges that guarantee the appearance of cracks in a precisely specified direction. The influence of the load scheme on the development of a splitting crack in holes with stress concentrators is presented. The model for the analysis of crack formation at the tops of stress concentrators is considered. Non-explosive methods of directional destruction of monoliths using special structures are described. Considered patents for static rock splitting. The results of destruction over a certain time are given. In addition, non-explosive mining of gabbroid rock blocks using destructive mixtures together with surface-active substances is considered.

The Effect of Impact Load on the Atomistic Scale Fracture Behavior of Nanocrystalline bcc Iron.

Nanocrystalline metals have many applications in nanodevices, especially nanoscale electronics in aerospace. Their ability to resist fracture under impact produced by environmental stress is the main concern of nanodevice design. By carrying out molecular dynamics simulations under different fast loading rates, this work examines the effect of impact load on the fracture behavior of nanocrystalline bcc iron at an atomistic scale. The results show that a crack propagates with intergranular decohesion in nanocrystalline iron. With the increase in impact load, intergranular decohesion weakens, and plastic behaviors are generated by grain boundary activities. Also, the mechanism dominating plastic deformation changes from the atomic slip at the crack tip to obvious grain boundary activities. The grain boundary activities produced by the increase in impact load lead to an increase in the threshold energy for crack cleavage and enhance nanocrystalline bcc iron resistance to fracture. Nanocrystalline bcc iron can keep a high fracture ductility under a large impact load.

Mechanics of structural size effect in impact brittle fracture of steels and consequent scaling laws for fracture

A large structural size effect on brittle fracture energy was observed in studies of impact fracture of steels by Stanton, Batson and Docherty, nearly 100 years ago. The size effect was seen in macroscopically brittle fractures of geometrically similar specimens tested over a large size range. These historical findings have great significance in designing large-scale steel structures such as ships and bridges. However, there has been no physical principle or theory yet to explain the size effects observed by Stanton, Batson and Docherty. In the present work, a new approach based on net-section mechanics is used to explain the size effect. It is shown that the change in net-section strain energy predicts well the size effect on fracture energy , under the constant condition of cleavage crack initiation stress at the notch root. The spectacular decrease in specific fracture energy with increased specimen size is explained by noting the three-dimensional nature of stored strain energy and the two-dimensional nature of fracture energy dissipated in the crack layer. By scaling both energies to a reference cubic specimen volume and equating, an expression that describes the inverse size dependence of specific fracture energy has been formulated. The mechanics of the size effect is illustrated by assessing the theory with extensive experimental data. Further, scaling laws for fracture energy have been developed. This work honours the pioneering studies of Stanton, Batson and Docherty, which have been instrumental for the development of the present theory and analysis.

Spallation damage of tungsten heavy alloy under shock loading

In this study, plate-impact experiments are conducted using tungsten heavy alloy (WHA) to obtain the free-surface velocity profiles under shock stress of 6–23 GPa. By analyzing the velocity wave profile, it is demonstrated that the spall strength is weakly dependent on the peak stress. The microstructure of the recovered WHA is well characterized and it’s observed that intergranular fracture and cleavage are the primary fracture mechanisms. Deformation twins are sparsely distributed near the cleavage crack. The existence of twin boundary not only affects crack propagation but also regulates the crack path and reinitiates the cleavage propagation direction on the twin boundary. The macroscopic cleavage facet planes are detected to be {100}, {110} and {111} at all shock stress.

Precipitation Kinetics of Water-Cooled Copper Mold Al-Mg-Si(-Mn, Zr) Alloy during Aging

The aging precipitation behavior of 6061 aluminum alloy that underwent iron casting and water-cooled copper casting and 6061 aluminum with Mn and Zr elements added was studied. Firstly, the hardness curves, tensile properties, and fracture morphology of four aging alloys—6061 (iron mold casting), 6061 (water-cooled copper mold casting), 6061-0.15Mn-0.05Zr (iron mold casting), and 6061-0.15Mn-0.05Zr (water-cooled copper mold casting)—were studied. The results of the aging hardness curve show that the aging precipitated phase of the 6061 alloy cast with a water-cooled copper mold is dispersed. The addition of Mn increases the amount of coarse inclusion α-(AlMnFeSi) in the alloy, resulting in a decrease in the age hardening property. The addition of Zr is related to the nucleation and growth of the G.P. region in the early aging period, mainly changing the formation rate and quantity of the G.P. region, leading to the advancement of peak aging and an increase in hardness. After the G.P. region gradually transforms into the β phase, the hardness of the alloy increases with the increase in the volume fraction of the β phase. When the β″ phase is coarsened to the point where the fault line can be bypassed, the transitional metastable β′ phase begins to precipitate, and the coherent distortion around it weakens, indicating over-aging. Finally, the equilibrium phase Mg2Si is formed. The results of the tensile tests indicate that the tensile strength and yield strength of the 6061-0.15Mn-0.05Zr alloy produced by water-cooled copper casting after aging are 356 Mpa and 230 Mpa, respectively. These values are 80 MPa and 75 MPa higher, respectively, than those of the 6061 aluminum alloy produced via iron casting. However, the elongation is by 5%. The fracture morphology of the tensile sample of the aging alloy shows that dislocation slip in the alloy results in dislocation plugging, stress concentration, and the initiation of crack cleavage on the surface. The fracture of the water-cooled copper mold-casting alloy is a ductile fracture of the microporous aggregation type, and the macroscopic fracture exhibits an obvious “neck shrinkage” phenomenon. The fracture analysis is consistent with the mechanical properties. The DSC curve shows that there is no enrichment process of solute atoms during the heating process, and the aging precipitation process after homogenization is as follows: G.P. zone → β″ phase → β′ phase. The aging precipitation process of the water-cooled copper casting alloy after homogenization treatment is as follows: β″ phase → β′ phase (no precipitation in the G.P. zone was observed). The results of the differential scanning calorimetry (DSC) analysis show that the main strengthening phase in the experimental alloy system is the β″ phase. The activation energies for the β″ phase precipitation were calculated and found to be 147 KJ/mol, 217 KJ/mol, 185 KJ/mol, and 235 KJ/mol, respectively. Additionally, a kinetic equation for the β″ phase precipitation during alloy aging was fitted.

Formation of boehmite through desilication of volcanic-ash-altered kaolinite and its retention for gallium: Contribution to enrichment of aluminum and gallium in coal

Multiple parting bands within Permo–Carboniferous coal that are generally enriched in critical metals in the northern North China have been confirmed to be altered from volcanic ash (tonsteins). The tonsteins and adjacent coal in some areas contain boehmite with varying contents. Whether or not the boehmite has a relationship with the volcanic-ash-altered kaolinite remains poorly understood. Herein, petrographical, mineralogical, whole-rock geochemical, and in-situ elemental analyses, combined with U–Pb–Hf isotopic analysis of zircon, were performed for the boehmite-bearing/rich partings and coal collected from the eastern edge of the Datong and Jungar coalfields. Except for the boehmite, well-ordered kaolinite is predominant in the parting samples, where the columnar/tabular and vermicular kaolinite are commonly present. Additionally, the zircons separated from the representative parting and coal samples are mostly igneous origin with only one age population of ca. 300 Ma, almost same with the depositional age of the coal, suggesting that the kaolinite in the inorganic constitutes of the investigated coal seams were mainly altered from volcanic ash. Numerous fine-grained boehmite exhibit textural features of replacement for columnar/tabular and vermicular kaolinite along the cleavage cracks in the parting samples, suggesting that such boehmite were formed from desilication of volcanic-ash-altered kaolinite. The tonsteins and coal along the eastern edge of the coalfields were uplifted and influenced by fault activities due to Indosinian and Yanshan orogeny, which were probably experienced intensive leaching by silica-undersaturated percolating water and groundwater, resulting in desilication of volcanic-ash-altered kaolinite and precipitation of residual Al as boehmite. The Ga, preserved in the alumina octahedral sheets of volcanic-ash-altered kaolinite, were retained by boehmite due to its very similar geochemical behavior with Al. The formation of boehmite and its retention for Ga made a contribution to the genesis of high–Al–Ga coal in the northern North China.

Influence of Heat Treatment on Microstructure and Mechanical Properties of Direct-Quenched Fe-0.06C-0.2Si-2.0Mn Steel

In this study, the effect of subsequent heat treatment applied to high-strength low-alloy steel (HSLA) on the structure–property relationships was investigated. Tempering and intercritical annealing processes are introduced to elucidate the influence of subsequent heat treatment on mechanical properties of direct-quenched Fe-0.06C-0.2Si-2.0Mn steel from a microstructural perspective. The tempering process results in a typical tempered martensite with uniformly dispersed cementite, whereas the intercritical annealing process forms a dual-phase microstructure composed of soft ferrite and hard martensite for the direct-quenched steel. In the intercritical annealed steel, a number of mobile dislocations at the interphase (martensite/ferrite) boundary significantly decrease the yield strength, and the large difference in strength between ferrite and martensite enhances work hardening. Charpy V-notch impact test results indicate that the tempering and intercritical annealing processes improved the absorbed energy by more than 100 J compared to the direct-quenched steel at room temperature, and at −50 °C, the intercritically annealed steel exhibited the highest absorbed energy of approximately 140 J. Additionally, the high fraction of high-angle grain boundaries and fine grains of the intercritically annealed steel increase the resistance to cleavage crack propagation, thereby reducing the ductile-to-brittle transition temperature.

Abrasive machining induced surface layer damage behavior and formation mechanism of monocrystalline β-Ga2O3: A comparative study of nanoindentation and nanogrinding

Beta-phase gallium oxide (β-Ga2O3) has garnered significant attention in recent years as an ultra-wide bandgap semiconductor material. However, its surface layer damage behavior and machining deformation mechanism remain poorly understood. In this work, a systematic comparative study was conducted through nanoindentation and nanogrinding for monocrystalline β-Ga2O3 (−201) crystal plane. Transmission electron microscopy is employed as the primary characterization method. The results show that the microstructural evolution patterns of monocrystalline β-Ga2O3 can be categorized into four stages, i.e. stacking faults, twins, slip bands, and cleavage cracks are observed sequentially. According to the tests results, subsurface damage diagram models based on nanoindentation and nanogrinding are established, both of which exhibit the above evolution patterns as the indentation depth and grit depth of cut increases. However, there are some differences. In the nanogrinding process, nanocrystals and amorphous layers were found near the ground surface, which are related to the high strain rate grinding conditions and the unique material properties of monocrystalline β-Ga2O3 with low stacking fault energy. The results in this work contribute to an enhanced understanding of the deformation characteristics of monocrystalline β-Ga2O3 at macro and micro scales, while offering valuable insights for achieving damage control in ultra-precision machining processes.

The effect of precipitates on the fracture behavior and tensile properties of Mg–14Gd–0.5Zr (wt.%) alloy

The effect of precipitation aging on the fracture behavior of cast Mg–14.23Gd–0.45Zr (wt.%) alloy at room temperature has been studied in this work. Uniaxial tensile and three-point bending tests were conducted on samples peak-aged at 175, 200, 225, and 250 ℃. Notably, samples aged at 175 ℃ and 200 ℃ exhibited premature fracture during the uniaxial tensile test. Through fractographic observations of the tensile test samples and electron backscattered diffraction (EBSD) analysis on the samples subjected to three-point bending tests, a preferential formation of cleavage cracks in samples aged at 175 ℃ and 200 ℃ was identified as the reason for their premature fracture. The X-ray diffraction (XRD) results and transmission electron microscopy (TEM) observations of precipitates indicate that the dominant strengthening precipitates in all peak-aged samples are of the β' phase, and their size significantly influences the formation of cleavage cracks. This phenomenon is attributed to the shearing mechanism of precipitates. Specifically, the smaller β' precipitates formed under the aging temperature of 175–200 ℃ are susceptible to dislocation shearing, leading to the formation of cleavage cracks. In contrast, the larger size of β' precipitates formed under the aging temperature of 225–250 ℃ provides resistance to shearing, resulting in the restrained formation of cleavage cracks and ultimately contributing to the enhancement of the ultimate tensile strength.

Micromechanics of cleavage fracture and the associated tongue formation in ferritic steel

The present work investigates the micro-mechanisms of cleavage fracture in a low carbon ferritic steel, subjected to Charpy impact test at low temperature. EBSD crack path analysis reveals {100} crystallographic plane as the predominant cleavage plane in ferrite, with occasional cracking along the secondary {110} cleavage plane. {110} cleavage cracking is particularly feasible when the {100} planes within a given grain exhibit significant twist angles with the preceding crack plane. Moreover, the fracture surface also exhibited numerous “tongue” like features that are intermittently aligned parallel to a common <110> crack front, as evidenced from the point EBSD analysis directly on the fracture surface. To illuminate the origin of such intermittent tongues, we performed molecular dynamics fracture simulation on a pure Fe single crystal, considering a (001) edge crack with a large [110] crack front. It was found that the development of intermittent tongues mainly originates from the intermittent nucleation of symmetric {112}<111> type twins across the entire crack front. Such intermittent twin nucleation results in a sinusoidal crack front, characterized by twin boundary cracking in one region and radial expansion of cleavage cracking in the adjacent regions, which can ultimately lead to the formation of tongues on the fracture surface. Finally, based on the simulation results and experimental observations, we propose a step by step mechanism that potentially explains the formation of intermittent tongues when a sufficiently large <110> straight crack front propagates along a {001} cleavage crack plane.

Formation of columnar/tabular and vermicular kaolinite in the crystal tonsteins within the Late Carboniferous Coal in the Datong Coalfield, Shanxi Province, North China

The Datong Coalfield, Shanxi Province, North China, is rich in high-grade coal-measure kaolin, primarily occurring as partings within the Late Carboniferous–Early Permian coal seams. There is a type of kaolinite-dominant coarse-grained parting similar to sandstone in appearance, whereas the phanerocrystalline minerals are columnar/tabular and vermicular kaolinite rather than terrigenous detrital minerals. The origins of the coarse-grained partings and the formation mechanism of the columnar/tabular and vermicular kaolinite remain ambiguous. Herein, petrographical, mineralogical, whole-rock geochemical, and zircon U–Pb–Hf isotopic studies of the coarse-grained partings were conducted to explore these issues. The zircons in the coarse-grained partings show typical features of magmatic origin and yield a single age group of very latest Carboniferous at ca. 300 Ma, indicating they were transformed from air-fall volcanic ash. Therefore, the coarse-grained partings are essentially crystal tonsteins. The wide range of negative εHf(t) values and arc-related tectonic affinity of the zircons genetically link the primary volcanic ash to the Late Paleozoic continental arc volcanoes that existed in the Inner Mongolia Paleo-Uplift, related to the southward subduction of the Paleo-Asian oceanic plate beneath the North China Block. Two orthogonal cleavages are generally observed on the columnar/tabular and vermicular kaolinite in the crystal tonsteins, contradicting the crystalline structure of kaolinite that belongs to a 1:1 type phyllosilicate with only one cleavage along its (001) lattice plane. These columnar/tabular and vermicular kaolinite are considered to be pseudomorphic kaolinite after plagioclase in the crystal-rich volcanic ash. When the crystal-rich volcanic ash fell into open and acidic peat-forming environments (mires), the low-pH water containing abundant organic acids and good water circulation conditions facilitate dissolution of plagioclase along the chemically unstable (001) lattice planes and leaching out of Na+, Ca2+, and much of silica. Simultaneously, the Al3+ or hydroxides of aluminum and silica recrystallized along the (001) lattice planes of plagioclase as the substrate, constraining layer-by-layer growth of large kaolinite platelets to eventually form pseudomorphic kaolinite. The cleavages perpendicular to the exclusive (001) cleavage of pseudomorphic kaolinite should be inherited from the twin planes and (010) cleavage cracks (if present) of plagioclase.

Determining the sequence of elimination of impurity ions from the surface of historical cold iron weapons

Confirming the authenticity of historical cold weapons and determining their age is an urgent problem in practical examination. One of the promising directions for its solution is the experimental study of the process of elimination of impurity ions from iron, which occurs throughout the long history of life. This paper describes a model that explains the sequence of elimination of impurity ions from near-surface parts of the metal. Deformation indicators of the crystal lattice of iron were calculated and sorted in order of decreasing ionic radius of the impurity chemical element. A diagram of the deformation effect of impurity chemical elements on the volume-centered crystal lattice of iron was constructed. Ions that are larger in diameter are more actively eliminated from the surface layers of the metal, while ions that are smaller are removed to a lesser extent. With the help of the authors’ methodology, a study of the chemical composition of the surface of collection samples of iron cold weapons of the 20th, 19th, and 18th centuries was carried out. It has been established that a metal alloy made in the recent past ‒ up to 100 years ‒ is characterized by a very active release of impurity chemical elements on the surface when it is heated. Iron weapons made up to 200 years ago have a significantly lower ability to release chemical impurities because most of the latter have already been eliminated. At the same time, samples of cold weapons of this age already have microdefects in the form of cleavage cracks and caverns, so their surface contains a significant number of compounds of eliminated chemical elements that have accumulated during the long history of their use. Older cold weapons, made 300 years ago or earlier, have impurity ions that are smaller than ferric ions, particularly silicon. The results of the research are important for the identification and authentication of historical iron cold weapons